1. Field of Invention
The present invention relates to a lock assembly, and more particularly to a lock enhancement arrangement which is dedicatedly designed to reinforce the intensity of conventional locks so as to prevent conventional locks from being damaged by an axial tension.
2. Description of Related Arts
Locks are used everywhere since they provide people with a sense of security. Generally, locks come in all shapes and sizes, with many innovative design variations. However, most locks are based on fairly similar concepts. For most of us, the most familiar lock is the standard dead-bolt lock installed on a front door. In a normal deadbolt lock, a movable bolt or latch is embedded in the door so it can be extended out the side. This bolt is lined up with a notch in the frame. When you turn the lock, the bolt extends into the notch in the frame, so the door can't move. When you retract the bolt, the door moves freely.
Obviously, a deadbolt lock's only job is to make it simple for someone with a key to move the bolt but difficult for someone without a key to move it.
Most deadbolts use a cylinder lock. A cylinder lock is a lock in which a cylinder must rotate in order to open the lock. In the cylinder lock, the key turns a cylinder, or a plug, which turns an attached cam. When the plug is turned one way, the cam pulls in on the bolt and the door can open. When the plug turns the other way, the cam releases the bolt and the spring snaps it into place so the door cannot open. This is to say that the turning cylinder slides the bolt forward and backward. Conclusively, a cylinder lock is a lock in which a cylinder must rotate in order to open the lock. The cylinder may be held in place by a variety of locking mechanisms. The most common mechanisms in modern use is the tumber lock.
Here, it is worth to mention that the cylinder lock utilizes specific engagement or disengagement between a plurality of pin-tumblers in the lock cylinder and the key's serrations correspondingly to control the locking and unlocking functions thereof.
As shown in FIG. 1, the conventional cylinder lock which is incorporated in a door usually comprises a lock unit 20 which has a key slot formed therein, a lock body 10 embedded into a door frame having a lock cavity for receiving the lock unit 20. Furthermore, the lock unit 20 is attached on a cam which is cable of driving the locking latch or bolt. So, as a result, the lock unit 20, upon being inserted with a predetermined key, is adapted to drive the locking latch to engage with a door frame. On the other hand, the lock unit 20 is also adapted to drive the locking latch to disengage with the door frame so that the door can be unlocked.
Inside a cylinder lock, there is a sort of puzzle, which only the correct key can solve. One of the most common puzzles is the pin-and-tumbler design. In this type of cylinder lock, an outer casing has a cylindrical hole in which the plug is housed. To open the lock, the plug must rotate.
The main components in the pin-and-tumbler design are a series of small pins of varying length. The pins are divided up into pairs. Each pair rests in a shaft running through the central cylinder plug and into the casing around the cylinder plug. Springs at the top of the shafts keep the pin pairs in position in the plug. When no key is inserted, the bottom pin in each pair is completely inside the plug, while the upper pin is halfway in the plug and halfway in the casing. The position of these upper pins keeps the plug from turning—the pins bind the plug to the casing.
Furthermore, the plug has a straight, shaped slot known as the keyway at one end to allow the key to enter the plug; the other end may have a cam or lever which activates a mechanism to retract a locking bolt. A series of holes, typically five or six of them, are drilled vertically into the plug. These holes contain key pins of various lengths, which are rounded to permit the key to slide over them easily. The correct key will position the pins in a pin-and-tumbler lock so that all of the lower pins rest in the cylinder plug and all of the upper pins rest in the casing. This allows the plug to rotate, thus opening the lock. When the key is not in the lock, the pins straddle the shear point, preventing the plug from rotating.
It is thus clear that the the lock unit is the by far the important part of the lock, like a heart to a human being. Its performance and safety directly determines the quality of the lock.
Unfortunately, this conventional cylinder lock has an observable drawback, which is susceptible to easy damage. Referring to the FIG. 1, the commonly used cylinder lock is illustrated. It is seen that the lock unit 20 is directly installed into a lock body 10 having a front cover A14 as shown in FIG. 1, as a result, the lock unit is directly biasing against the front cover A14. I.e. the front cover A14 is bearing most of axial thrust force from the lock unit A20. Moreover, since the outer casing of the lock unit A20 has several vertical shafts for holding the spring-loaded pins, the outer casing further comprises a crester portion A21 protudingly extended from the outer casing of lock unit A20. Actually, it is the front end A21a of the crester portion A21 which is directly biasing the front cover A14 of the lock body 10, so that the front end A21a of the crester portion 21 is capable of creating an enormous intensity of pressure on the front cover A14. However, sometimes, the front cover A14 is relatively thin and weak to withstand such a huge pressure. So the front cover A14 is susceptible to be cracked and vulnerable to be broken off thus causing the lock unit A20 be pull out from the lock body A10.
Very often, the front cover A14 is not strong enough both in terms of the materials used and its structure so that a potential intruder, by vigorously breaking the front cover A14 of the lock boy 10, can be able to pull out the lock unit 20 from the lock body 10 and destroy the door lock.
We now are living in a security aware society. The lock, as its name implies, has to play a more important role to protecting properties. It is witnessed that governments had enacted more and more rigorous standard for the tensile strength of the cylinder lock having a lock unit. For example, the United States of America issued the BHMA (Builders Hardware Manufacturers Association) categorizing an anti-twist ability and an impact resistance of a regular door lock as each having three distinct levels, namely first class (11000N), second class(4800N), and third class(2300N) respectively. Unfortunately, most conventional door locks fail to achieve the first class standard since there are no tension reinforcement structure have been applied for protecting the lock unit at all.
Because of the inherent structural features of conventional cylinder locks as mentioned above, a stronger and more secure lock is definitely required for preventing the lock unit from being pulled out from the lock body.